The 33 miners trapped 700 metres underground in a collapsed mine in Chile are expected to work in 12-hour shifts to help dig themselves out because they will be faced with a constant hail of falling rocks that is expected to last for months.

The rescue plan calls for a drilling rig, an Australian machine known as a Strata 950, to bore a hole into a chamber astride the workers' refuge. It will then be enlarged, producing a cascade of rocks and debris.

"Making this hole is easy … Though this is a huge machine, it is not particularly difficult to operate," said one of the rig operators. "It will take time because of the number of metres."

An estimated 500kg of rocks and other debris will rain down on the gallery floor every hour. The trapped workers are expected to use heavy machinery and shovels to keep the duct clear. With dust already a problem for their eyes and lungs, officials are designing systems to confine the debris and dust away from the main living, cooking and sanitary facilities now being developed for the workers.

"We have asked them to design a map of the area," said Jaime Manalich, the Chilean minister of health. Then the rescue co-ordinators will try to institute a rigid system of hygiene, exercise, entertainment and communications.

Manalich held a 90-minute conversation with Nasa engineers on Wednesday and said a team of its specialists would be brought to the mine to monitor the miners' health and welfare. He said Nasa's expertise was vital to maintaining their mental and physical health for the next 90 days. "Nasa told us that we need to give them four litres a day of water, given the extreme heat and humidity."

As health officials scramble to keep the trapped miners under constant medical surveillance, one of the men, Johny Berrios, was named medical co-ordinator.

"He always wanted to be a doctor," said his wife, Marta Salinas, in her tent pitched by the mouth of the San Jose mine. "He reads so much and he really knows everything about medicine. He always would give injections to his mother and was constantly reading about this."

Rescue leaders have decided Berrios is the most qualified to administer medicine, co-ordinate patient charts and serve as lead interlocutor for health issues.

With the men's health now stabilising, solid food has been delivered: energy bars were sent down on Wednesday. Given the limitations of the delivery system – a 700-metre tube no wider than the inside of a toilet roll – ingenious systems are being developed to provide them with as normal an existence as possible.

A miniature home-theatre system is ready for delivery, although psychologists are still deciding on appropriate movies.

As lawyers filed a suit against the mine owners, a judge in Copiapo issued an order to freeze some $2 million in assets. "They said they did not have the money to pay salaries," said Remberto Valdes Hueche, a lawyer representing several of the families."But we have been working hard to identify their assets and found they do have money."

Since the disaster, officials have been scouring the country for illegal mines. Chile is the world's leading producer of copper and hundreds of abandoned mines that were not profitable are now being opened again – both legally and as clandestine operations – after its price trebled.

Chilean officials shut down 18 mines following the San Jose accident. Another 300 are expected to be ordered to close.

"I am afraid there is going to be an indiscriminate shutting of small mines," said Luciano Pinto, president of the Tierra Amarilla mining association, which operates in the same area as the San Jose mine. "We are aware that they [government] are going to come in with a hard hand and the result is that the small mining operations are going to pay for what the mid-sized mining operations [like San Jose] have produced."